fix: invalid Fortran continuation in m_ibm.fpp breaks Cray ftn build

Line ending with & followed by a continuation line with only & and a comment
is non-standard. Cray ftn (ftn-71) rejects it. Move the comment to its own line.

Author: sbryngelson

src/simulation/m_ibm.fpp

@@ -1179,8 +1179,8 @@ contains
         else  ! we do not have an analytic moment of inertia calculation and need to approximate it directly via a sum
             count = 0
             moment = 0._wp
-            cell_volume = (x_cc(1) - x_cc(0))*(y_cc(1) - y_cc(0)) &
-                           &  ! computed without grid stretching. Update in the loop to perform with stretching
+            ! computed without grid stretching; update in the loop to perform with stretching
+            cell_volume = (x_cc(1) - x_cc(0))*(y_cc(1) - y_cc(0))
             if (p /= 0) then
                 cell_volume = cell_volume*(z_cc(1) - z_cc(0))
             end if